In a past invention, a surface on an outlet side of a fuel injection hole has a coarse surface roughness and a cross-sectional area on the outlet side of the fuel injection hole is larger than a cross-sectional area on an inlet side. This causes active accumulation of deposit on an outlet portion of fuel to decrease adherence of deposit on the inlet side (measuring portion) of the fuel.
In another past invention, radially-shaped grooves are formed on a lower end face (on a fuel outlet side of a fuel injection hole) of a fuel injection valve to guide fuel from a fuel outlet of the injection hole toward an outer peripheral side. Thus, retention of the fuel around the fuel outlet and accumulation of deposit in accordance with the retention of the fuel are reduced.